answer: option c is correct
we know tha tcos(a-b) = cosa cosb + sinasinb
plugging a = 180 and b = ф
= (-1) cosф+ (0) sinф [ since cos180=-1 and sin180 =0]
= -cosф + 0
therefore option c is the correct answer.
the reflex angle is the larger of two angles.
reflex + obtuse = 360 set reflex = 220
220 + obtuse = 360 subtract 220 from each side
obtuse = 140
(it is actually 51.11, but since you're rounding it will be 51)
a.)3m, 6m, 3m